Method of winding a stator core with a continuous conductor having a rectangular cross-section and a stator core

ABSTRACT

A method of inserting a continuous conductor having a rectangular cross-section into slot segments formed in a stator core includes forming a core member having a plurality of slot segments each having an opening and inserting a stator winding having a plurality of phases into select ones of the slot segments. Each of the plurality of phases has at least one conductor including a plurality of substantially straight segments alternately connected by a plurality of end loop segments. A section of the at least one conductor includes three consecutive end loop segments and three consecutive straight segments formed from a single continuous conductor. The method further includes narrowing the opening of each of the plurality of slot segments by forming an annular stator core having a central axis. The three consecutive straight segments are substantially similarly radially spaced from the central axis.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of U.S. application Ser. No.13/298,813 filed Nov. 17, 2011, the disclosure of which is incorporatedby reference herein its entirety.

BACKGROUND OF THE INVENTION

Exemplary embodiments pertain to the art of electric machines and, moreparticularly, to a method of winding a stator core with a continuousconductor having a rectangular cross-section.

At present, many electric machines include stator cores that are woundwith wire having a circular cross-section. The stator core is heldstationary and the wire is fed through a winding needle that is rotatedabout a stator tooth. Once the stator tooth is wound, the wire isadvanced to a subsequent stator tooth. At each tooth, the winding needlenot only travels along a circular path but also moves in and out tolayer the wire. Upon exiting the winding needle, the wire twists as aresult of rotational forces developed while traveling along the circularpath.

In other cases, the stator core is wound with wire having a rectangularcross-section. A continuous wire is laid into slot segments formed inthe stator core. In this manner, the wire is not subjected to twisting.The use of rectangular wire increases a fill volume of the slot segmentswhich, in turn, enhances electrical properties of the stator. Electricalproperties of the stator are further enhanced by adding tooth elementsto the slot segments. The tooth elements reduce torque ripples duringstart-up of the electric machine. However, the tooth elements alsocreate a localized narrowing of the slot segments. The localizednarrowing precludes the use of a continuous wire having a rectangularcross-section. In such cases, the wire is formed into discrete sections,or hairpins, that are axially inserted into the slot segments. Once allsections are inserted, select ones of the sections are joined to formone or more phase windings for the stator.

BRIEF DESCRIPTION OF THE INVENTION

Disclosed is a method of inserting a continuous conductor having arectangular cross-section into slot segments formed in a stator coreincludes forming a core member extending from a first end portion to asecond end portion and a plurality of slot segments each having anopening and inserting a stator winding having a plurality of phases intoselect ones of the slot segments. Each of the plurality of phases has atleast one conductor including a plurality of substantially straightsegments alternately connected by a plurality of end loop segments. Asection of at least one conductor includes three consecutive end loopsegments and three consecutive straight segments formed from a singlecontinuous conductor. The method further includes narrowing the openingof each of the plurality of slot segments by forming an annular statorcore having a central axis. The three consecutive straight segments aresubstantially similarly radially spaced from the central axis.

Also disclosed is a stator core including a core member having a firstend portion that extends to a second end portion through a first surfaceand an opposing second surface. The core member includes a first axialend, a second axial end and a central axis. A plurality of slot segmentsis formed in the core member. Each of the plurality of slot segmentsincludes first and second wall portions spaced one from another todefine a first width of the plurality of slot segments. Each of thefirst wall portions includes a first end portion, a second end portion,and a tooth element arranged at the second end portion, and each of thesecond wall portions includes a first end section, a second end section,and a tooth member at the second end section. The tooth element on eachfirst wall portion extends toward the tooth member on each second wallportion to define a second width of the slot segment. The stator corealso includes a stator winding having a plurality of phases. Each of theplurality of phases has at least one conductor including a plurality ofsubstantially straight segments disposed in select ones of the pluralityof slot segments. The straight segments are alternately connected at thefirst and second axial ends of the core member by a plurality of endloop segments. A section of the at least one conductor includes threeconsecutive end loop segments and three consecutive straight segmentsformed from a single continuous conductor. The three consecutivestraight segments are substantially similarly radially spaced from thecentral axis.

Further disclosed is an electric machine including a housing, a rotorrotatably supported within the housing, and a stator fixedly mountedrelative to the rotor. The stator includes a stator core including acore member having a first end portion that extends to a second endportion through a first surface and an opposing, second surface, thecore member including a central axis, a first axial end and a secondaxial end. A plurality of slot segments is formed in the core member.Each of the plurality of slot segments includes first and second wallportions spaced one from another to define a first width of theplurality of slot segments. Each of the first wall portions includes afirst end portion, a second end portion and a tooth element arranged atthe second end portion, and each of the second wall portions includes afirst end section, a second end section, and a tooth member at thesecond end section. The tooth element on each first wall portion extendstoward the tooth member on each second wall portion to define a secondwidth of the slot segment. The stator core further includes a statorwinding having a plurality of phases. Each of the plurality of phaseshas at least one conductor including a plurality of substantiallystraight segments disposed in select ones of the plurality of slotsegments. The straight segments are alternately connected at the firstand second axial ends of the core member by a plurality of end loopsegments. A section of the at least one conductor includes threeconsecutive end loop segments and three straight segments formed from asingle continuous conductor. The three consecutive straight segments aresubstantially similarly radially spaced from the central axis.

BRIEF DESCRIPTION OF THE DRAWINGS

The following descriptions should not be considered limiting in any way.With reference to the accompanying drawings, like elements are numberedalike:

FIG. 1 depicts a cross-sectional view of an electric machine including astator core, in accordance with an exemplary embodiment;

FIG. 2 depicts a perspective view of the stator core of FIG. 1;

FIG. 3 depicts a perspective view of a stator core member prior toinsertion of stator windings, in accordance with an exemplaryembodiment;

FIG. 4 depicts a perspective view of the stator core member of FIG. 3receiving stator windings, in accordance with an exemplary embodiment;

FIG. 5 depicts a perspective view of the stator core member followinginsertion of the stator windings, in accordance with an exemplaryembodiment;

FIG. 6 depicts a fragmentary perspective view of a layer of end loopsegments of a stator winding, in accordance with another aspect of anexemplary embodiment;

FIG. 7 depicts a perspective view of a plurality of layers of end loopsegments of FIG. 6;

FIG. 8 depicts a perspective view of a plurality of layers of end loopsegments of FIG. 7 having a plurality of straight segments and aplurality of end loop segments; and

FIG. 9 depicts a schematic view of a stator core illustrating locationsof the plurality of layers of the end loop segments of FIG. 8.

DETAILED DESCRIPTION OF THE INVENTION

A detailed description of one or more embodiments of the disclosedapparatus and method are presented herein by way of exemplification andnot limitation with reference to the Figures.

An electric machine, in accordance with an exemplary embodiment, isindicated generally at 2, in FIG. 1. Electric machine 2 includes ahousing 4 having first and second side walls 6 and 7 that are joined bya first end wall 8 and a second end wall or cover 10 to collectivelydefine an interior portion 12. First side wall 6 includes an innersurface 16 and second side wall 7 includes an inner surface 17. At thispoint it should be understood that housing 4 could also be constructedto include a single side wall having a continuous inner surface.Electric machine 2 is further shown to include a stator 24 arranged atinner surfaces 16 and 17 of first and second side walls 6 and 7. Stator24 includes an annular stator core 28 which, as will be discussed morefully below, supports a plurality of stator windings 30.

Electric machine 2 is also shown to include a shaft 34 rotatablysupported within housing 4. Shaft 34 includes a first end 36 thatextends to a second end 37 through an intermediate portion 39. First end36 is rotatably supported relative to second end wall 10 through a firstbearing 43 and second end 37 is rotatably supported relative to firstend wall 8 through a second bearing 44. Shaft 34 supports a rotorassembly 50 that is rotatably mounted within housing 4. Rotor assembly50 includes a rotor hub 54 that is fixed relative to intermediateportion 39 of shaft 34, and a rotor lamination 59 that is configured torotate relative to stator 24.

As best shown in FIGS. 2 and -3, stator core 28 is formed from a coremember 69 having a first end 70 that extends to a second end 71 throughan intermediate portion 72. Intermediate portion 72 includes a firstsurface 73 and an opposing, second surface 74. In the exemplaryembodiment shown, core member 69 includes a plurality of slot segments,one of which is indicated at 80, that receive stator windings 30, aswill be detailed more fully below. Each slot segment 80 includes a firstwall portion 82 and an opposing, second wall portion 83 that areseparated by a base portion 85 which establishes a first width 87. Firstwall portion 82 includes a first end portion 92 that extends from baseportion 85 to a second end portion 93. Second end portion 93 includes atooth element 95.

Similarly, second wall portion 83 includes a first end section 97 thatextends from base portion 85 to a second end section 98. Second endsection 98 includes a tooth member 100. Tooth member 100 is spaced fromtooth element 95 to establish an opening 102 having a second width 104of slot segment 80. Tooth member 100 and tooth element 95 are positionedon stator core 28 so as to reduce torque ripple effects associated withstarts and stops of electric machine 2. Core member 69 is also shown toinclude a plurality of recesses 108 formed in second surface 74 as wellas a plurality of cooling passages, one of which is shown at 111.Recesses 108 provide flexibility to core member 69 that allows theinsertion of a number of continuous conductors 114-119 into slotsegments 80. Continuous conductors 114-119 collectively define statorwindings 30. Of course it should be understood that the number ofcontinuous conductors may vary.

In accordance with the exemplary embodiment, continuous conductors114-119 have a rectangular cross-section that is larger than secondwidth 104. Therefore, in order to insert continuous conductors 114-119into slot segments 80, second width 104 is temporarily widened. As bestshown in FIG. 4, prior to inserting continuous conductors 114-119, coremember 69 is deformed in a first direction causing each opening 102 towiden to a third width 124. More specifically, core member 69 isdeformed such that first surface 73 has a generally convex curvature andsecond surface 74 has a generally concave curvature. At this point,continuous conductors 114-119 are installed into select ones of theplurality of slot segments 80 to establish stator windings 30. Once allconductors are inserted, core member 69 is deformed in a seconddirection, opposite to the first direction causing opening 102 to narrowto a fourth width 128 that is smaller than second width 104, such asshown in FIG. 5. More specifically, core member 69 is deformed so as tocause first end 70 to contact second end 71 to form an annular ring 130(FIG. 2). First end 70 is secured to second end 71 through, for example,welding, and select ones of continuous conductors 114-119 areinterconnected to establish a desired wiring configuration for statorwindings 30 and complete stator core 28.

Reference will now follow to FIGS. 6-8 in describing a stator winding200 in accordance with another aspect of an exemplary embodiment. Statorwinding 200 includes an end loop segment 242 including a firstsubstantially straight end portion 244 and a second substantiallystraight end portion 246 that are each proximate to a respectivestraight segment, discussed in more detail below. First end portion 244and second end portion 246 of the end loop segment 242 are at a samesubstantial radial distance from a central axis 247 (FIG. 9) of thestator core 48 and therefore will be in the same radial position. Twostraight segments connected to end portions 244 and 246 will thereforealso be at substantially the same radial distance from central axis 247of stator core 48 and will therefore be housed in the same radialposition. The radial position is determined to be the position of thestraight segment with respect to the other straight segments in a coreslot. For example, in one core slot, the outermost straight portion isconsidered to be housed in the outermost radial position, the secondoutermost straight portion is considered to be housed in the secondoutermost radial position and so forth. The radial position of astraight segment is a relative position and not a distance. First endportion 244 and second end portion 246 form a portion of a layer,indicated generally at 248, of the stator winding 200 whose straightsegments are in a same radial distance (and radial position) from thecentral axis 247 of stator core 48.

End loop segment 242 includes a first sloped portion 250 and a secondsloped portion 252 that meet at an apex portion 254. First slopedportion 250 is substantially co-radial with the layer 248, first endportion 244 and second end portion 246. Second sloped portion 252 issubstantially non-co-radial with the layer 248, first end portion 244and second end portion 246. Apex portion 254 includes a first radialextension portion 256. First radial extension portion 256 extends fromfirst sloped portion 250 in a radially outward direction, which providesa radial outward adjustment for end loop segment 242. A second slopingradial extension portion 258 connects second sloped portion 252 andsecond end portion 246. Second radial extension portion 258 extends fromsecond sloped portion 252 in a radially inward direction, which providesa radial inward adjustment for the end loop segment 242. While the endloop segment 242 has been shown wherein the radial outward adjustment isadjacent apex portion 254 and the radial inward adjustment is adjacentsecond sloped portion 252, those skilled in the art can appreciate thatthe radial outward and inward adjustments can be on any one, or on anytwo, of first sloped portion 250, second sloped portion 252, and apexportion 254 in order to provide a cascaded winding pattern, described inmore detail below.

End loop segment 242 is shown adjacent a plurality of substantiallyidentical end loop segments, indicated generally at 260 and 262. Endloop segments 242, 260, and 262 form a portion of stator winding 200.End loop segments 242, 260, and 262 are shown in a three-phase windingpattern but those skilled in the art will appreciate that the end loopsegments 242, 260, and 262 may be formed in, for example, a six-phasewinding pattern, or any other winding pattern advantageous for producingelectricity or for generating torque, as in the case of an electricmachine. End loop segments 242, 260, and 262 are preferably eachdisposed at a first axial end 263 of stator core 48.

Second end portion 246 attaches to a first straight segment, shownschematically at 264, which extends through one of slot segments 80 tosecond axial end (not separately labeled) of stator core 48. As firststraight segment 264 exits the second end, first straight segment 264 isattached to an end of another end loop segment, shown schematically at266, which is substantially identical to end loop segments 242, 260, and262. End loop segment 266 is attached at another end (not shown) to asecond straight segment, shown schematically at 268. Second straightsegment 268 extends upwardly through another one of the slot segments 80of stator core 48 and attaches to a portion 244 a of an end loop segment242 a, which is substantially identical to the end loop segments 242,260, and 262. End loop segments 242, 266 and 242 a are considered asthree consecutive end loop segments because end loop segments 242 and266 are connected to the same straight segment 264 and end loop segments266 and 242 a are connected to the same straight loop segment 268.Straight segments 264 and 268 are considered consecutive straightsegments because straight segment 264 is connected to end loop segment266, which is also connected to straight segment 268. Similarly, aportion 246 a of end loop segment 242 a connects to another straightsegment, discussed in more detail below. The pattern of connecting endloop segments 242, 266, and 242 a and straight segments, such as thestraight segments 264 and 268, as outlined above, continues throughoutone substantial pass about a circumference of stator core 48 to form afirst layer, such as layer 248, of a single phase of the stator winding200.

End loop segment 242 a is shown adjacent a plurality of substantiallyidentical end loop segments, indicated generally at 260 a and 262 a. Endloop segments 242 a, 260 a, and 262 a are each connected to acorresponding plurality of straight segments, discussed in more detailbelow, such as the straight segments 264 and 268, which are eachdisposed in a respective slot segment 80 of the stator core 48. Straightsegments 264 and 265 are attached to a plurality of end loop segments,discussed in more detail below, that are substantially identical to theend loop segments 260, 260 a, 262, 262 a, and 266. End loop segments260, 260 a, 262, and 262 a, when attached to straight segments and endloop segments, each form a respective continuous first layer 248 of thephase of the complete stator winding 200 that is wound about stator core48.

Preferably, each straight segment 264 and 268 and each end loop segmentportion 242, 242 a, 260, 260 a, 262, 262 a, and 266 are formed from arectangular wire and have a cross-sectional shape having a substantiallyequal area, however, other shapes could also be employed such as roundor square. For those skilled in the art, it is known that typicalrectangular or square shaped conductors may include radii on the cornersintermediate two adjacent edges.

Referring now to FIGS. 7 and 8, the first layer 248 of the end loopsegments 242, 242 a, 260, 260 a, 262, 262 a of FIG. 6, is shown with asecond layer of end loop segments, indicated generally at 269. Secondlayer 269 is located radially inward of first layer 248 at apredetermined radial distance from layer 248. Second layer 269 includesa plurality of end loop segments, indicated generally at 270, 273, and275. Together, layers 248 and 269 form a portion of stator winding,indicated generally at 200. The conductor of second layer 269 includingend loop 270 is similar than that of the conductor of first layer 248including end loop 242 except that it is inserted into the slot segments80, shifted by n slots, discussed in more detail below, and it has endloop segments, such as the end loop segment 270, that extend radiallyoutwardly in a counterclockwise direction 276, which is opposite the endloop segments, such as the end loop segment 242, of first layer 248,which extend radially outwardly in a clockwise direction 277.

End loop segment 270 includes a first sloped portion or non-co-radialportion 278 and a second sloped portion 279 connected by an apex portion280. First sloped portion 278 is substantially co-radial with secondlayer 269, first end portion 272 and second end portion 274. Secondsloped portion 279 is substantially non-co-radial with second layer 269,first end portion 272 and second end portion 274. Apex portion 280includes a first radial extension portion 282. First radial extensionportion 282 extends from first sloped portion 278 in a radially outwarddirection, which provides a radial outward adjustment for end loopsegment 270. A second sloping radial extension portion 284 connectssecond sloped portion 279 and second end portion 274. Second radialextension portion 284 extends from second sloped portion 279 in aradially inward direction, which provides a radial inward adjustment forend loop segment 270.

As can best be seen in FIG. 7, the non-co-radial portion 278 of end loopsegment 270 extends radially outward where it becomes substantiallyco-radial with first layer 248, first end portion 244 and second endportion 246, but because it is shifted by n slots, discussed in moredetail below, non-co-radial portion 278 does not violate the space ofend loop segments of first layer 248. This allows end loop segments offirst and second layers 248 and 269 to cascade together forming a twolayer winding 200, which extends radially outward by one wire widthbeyond first layer 248 but does not extend radially inward beyondinnermost or second layer 269. For a winding with a plurality of layers,a third layer (not shown) which is substantially identical to the firstlayer 248, would have non-co-radial portions that would extend radiallyoutward and be substantially co-radial with second layer 269 andtherefore cascade with the second layer 269. For a pattern where theradial layers alternate between being substantially identical with firstlayer 248 and then second layer 269, a pattern develops where thewinding only extends radially outward by one wire width of the outermostor first layer 248 but not radially inward of the innermost layer 269.This cascading effect allows a winding 200 with a plurality of layers tobe inserted into a stator core, such as the stator core 48, that extendradially outwardly by one wire width while not extending radiallyinwardly. End loop segments 273 and 275 are substantially identical toend loop segment 270. The radial outward and inward adjustments forfirst and second layers 248 and 269 form a cascaded winding patternshown in FIGS. 7 and 8.

Referring now to FIG. 8, first layer 248 and second layer 269 are shownwith a plurality of straight segments 288, which are substantiallyidentical to straight segments 264, 265, and 268. In accordance with anaspect of an exemplary embodiment, three consecutive straight segments288 of first layer 269 are spaced substantially similarly radially fromcentral axis 247 a first distance. Likewise, three consecutive end loopsegments 288 of second layer 269 are spaced substantially similarlyradially from central axis 247 a second distance. End loop segment 266of FIG. 6 is shown having a first sloped portion 289 and a second slopedportion 290 connected by an apex portion 291. First sloped portion 289is substantially co-radial with the first layer 248, and straightsegments 264 and 268. Second sloped portion 290 is substantiallynon-co-radial with the first layer 248, and straight segments 264 and268. Apex portion 291 includes a first radial extension portion 292.First radial extension portion 292 extends from first sloped portion 289in a radially outward direction, which provides a radial outwardadjustment for the end loop segment 266. A second sloping radialextension portion 293 connects second sloped portion 290 and straightsegment 268. Second radial extension portion 293 extends from secondsloped portion 290 in a radially inward direction, which provides aradial inward adjustment for the end loop segment 266. End loop segments294 and 295 are substantially identical to the end loop segment 266.

Similarly, an end loop segment 296 of second layer 269 is shown adjacentthe end loop segment 295 of first layer 248. End loop segment 296includes a first sloped portion 350 and a second sloped portion 351connected by an apex portion 352. First sloped portion 350 issubstantially co-radial with second layer 269, and straight segments 288of second layer 269. Second sloped portion 351 is substantiallynon-co-radial with second layer 269, and straight segments 288. Apexportion 352 includes a first radial extension portion 353. First radialextension portion 353 extends from first sloped portion 350 in aradially outward direction, which provides a radial outward adjustmentfor end loop segment 296. A second sloping radial extension portion 354connects second sloped portion 351 and straight segment 288. Secondradial extension portion 354 extends from second sloped portion 351 in aradially inward direction, which provides a radial inward adjustment forend loop segment 296. End loop segments 297 and 298 are substantiallyidentical to the end loop segment 296.

Straight segments 264, 265, 268, and 288 of each phase of the statorwinding 200 are preferably disposed in respective slot segments 80 at anequal pitch around the circumference of stator core 48. Specifically, astraight segment of a phase, such as straight segment 264, is disposedin a respective slot segment 80 adjacent straight segment 265 of theadjacent phase. The respective straight segments 264 and 265 are spacedapart by a circumferential distance or pitch 263, best seen in FIG. 6.Circumferential pitch 263 is substantially equal to a circumferentialdistance between a pair of adjacent slot segments 80 in stator core 48.Each of the straight segments and end loop segments of the phaseincluding straight segment 264 remain disposed adjacent the respectivestraight segments and end loop segments of the phase including straightsegment 264 at the same circumferential pitch 263 throughout the lengthof the stator winding 200 and throughout the circumference of statorcore 48.

While straight segments 288 are shown generally coplanar in FIGS. 7 and8 for illustrative purposes, straight segments 288 are preferablyadapted to be received by a radially curved surface, such as an interiorsurface of stator core 48 and, therefore, are not coplanar (i.e., thecircumferential first layer 248 is shown flattened in, for example, FIG.7 but are co-radial). The width of each of straight segment 288,including any insulation, preferably fits closely to a width of slotsegments 80, including any insulation.

FIG. 9 depicts a plan schematic view of a stator core 48, in accordancewith an aspect of an exemplary embodiment. The stator core 48 includes atotal of thirty-six slot segments 80 numbered from 401 through 436 inincreasing number in the circumferential counterclockwise direction 276.Stator winding 200 is adapted to be inserted in the slot segments 80 toform a stator winding, in accordance with the present invention asfollows, where: n equals the number of phases in the stator winding 200.In FIG. 9, n=3.

When stator winding 200 is formed, a first lead (not shown) thatconnects to first end portion 244 is inserted into the second axial end(not separately labeled) of the stator core 48 in slot segment 401 andextends from the first axial end 263 of the stator core 48 in slotsegment 401. The straight and portion 246 is located in slot segment 434and end loop segment 242 connects first end portion 244 and straight endportion 246 at first axial end 263 of stator core 48. Straight endportion 246 connects to straight segment 264 in slot segment 434.Straight segment 264 extends through slot segment 434 and exits statorcore 48 at slot segment 434, where it connects to the end loop segment266. End loop segment 266 is substantially identical to end loop segment242 except that it connects straight segment 264 exiting from slotsegment 434 with straight segment 268 exiting from the slot segment 431and is located on the second axial end of stator core 48.

The subsequent end loop segments alternate locations on the opposingaxial ends of stator core 48 and connect straight portions in every nthslots. The straight portions of the end loop segments are located asfollows: a straight portion 246 a is located in slot segment 428, astraight portion 244 b is located in slot segment 425, a straightportion 246 b is located in slot segment 422, a straight portion 244 cis located in slot segment 419, a straight portion 246 c is located inslot segment 416, a straight portion 244 d is located in slot segment413, a straight portion 246 d is located in slot segment 410, a straightportion 244 e is located in slot segment 407, and a straight portion 246e is located in slot segment 404. Each of the straight portions 244-244e and 246-246 e, together with the associated end loop segments, form acontinuous conductor of one phase of the stator winding 200. Straightportion 246 e extends from a second axial end (not separately labeled)of the stator core 48 as a second lead (not shown) and completes firstlayer 248 of the continuous phase. The first lead of the first layer248, therefore, extends from slot segment 401 and the second lead of thephase extends from slot segment 404. Each of the first and second leadsis located on the second axial end (not separately labeled) of thestator core 48.

Second layer 269 of the phase lays radially inward of first layer 248and is shifted by n slots, such that the respective end loop segmentsare on the opposite axial ends of stator core 48 at the respective endloop segments of first layer 248.

A first lead that connects to second end portion 274 is inserted intothe second axial end of stator core 48 in slot segment 434 and extendsfrom the first axial end 263 of stator core 48 in slot segment 434.First end portion 272 is located in slot segment 431 and end loopsegment 270 connects the first and second end portions 272 and 274 atthe first axial end 263. First end portion 272 connects to a straightsegment, such as the straight segment 288, in slot segment 431. Straightsegment 288 extends through slot segment 431 and exits the second axialend of stator core 48 at slot segment 431, where it connects to an endloop segment, such as the end loop segment 296 of FIG. 8, that issubstantially identical to the end loop segment 270 except that itconnects the straight segments exiting from slot number 431 with anotherstraight segment 288 exiting from slot segment 428 and is located on thesecond axial end of stator core 48.

Similar to first layer 248, the subsequent end loop segments alternatelocations on first axial end 263 and the second axial end of stator core48 and connect straight portions in every nth slots. The straightportions of the end loop segments are located as follows: a straightportion 274 a is located in slot segment 428, a straight portion 272 ais located in slot segment 425, a straight portion 274 b is located inslot segment 422, a straight portion 272 b is located in the slotsegment 419, a straight portion 274 c is located in slot segment 416, astraight portion 272 c is located in slot segment 413, a straightportion 274 d is located in slot segment 410, a straight portion 272 dis located in slot segment 407, a straight portion 274 e is located inslot segment 404, and a straight portion 272 e is located in slotsegment 401. Each of the straight portions 272-272 e and 274-274 e,together with the associated end loop segments, form a continuous phaseof the stator winding 200. The straight portion 272 e extends from thesecond axial end of stator core 48 as a second lead (not shown) andcompletes second layer 269 of the continuous phase. The first lead ofsecond layer 269, therefore, extends from slot segment 434 and thesecond lead of the phase extends from slot segment 401. Each of thefirst and second leads is located on the second axial end of stator core48. Preferably, the first and second leads of first and second layers248 and 269 are connected to a rectifier (not shown), for supplying DCpower to an automotive battery (not shown).

Each of the respective end loop segments 242, 260, 262, 266, 270, 273,275, 294, 295, 296, 297, and 298 of the conductors of the stator winding200 are cascaded, meaning that for each pass around the stator core 48,each of the conductors can be inserted into the stator core 48 in asequential order. For example, the conductor including the end loopsegment 242 is inserted for one substantial revolution about thecircumference of stator core 48. After the conductor including end loopsegment 242 is inserted, the conductor including end loop segment 260may be inserted for one substantial revolution about the circumferenceof stator core 48. This pattern is repeated for the conductor includingthe end loop segment 262. As seen in FIG. 8, when the conductors areinserted in this manner, the entirety of each of the continuousconductors may be wound about the circumference of stator core 48without interfering with any of the other conductors. Preferably, theconductors of the first and second layers 248 and 269 are aligned in oneradial row in each slot segment 80.

The conductor including end loop segment 242 of first layer 248, and theconductor including end loop segment 270 of second layer 269, includestraight segments which coexist in the same slot segments, as can bestbe seen in FIG. 7. Therefore, these two conductors are the conductors ofone phase. Furthermore, because each conductor passes circumferentiallyonce around stator core 48, the phase of a winding with first and secondlayers 248 and 269 is comprised of two conductors, each passing oncecircumferentially around stator core 48. Similarly, the two conductorsincluding end loop segments 260 and 273 coexist as a second phase andthe conductors including end loop segments 262 and 275 coexist as athird phase, best seen in FIG. 7.

Alternatively, first and second layers 248 and 269 of one particularphase are formed from one single continuous conductor. The phase windsaround the stator core 48, alternating end loop segments with straightsegments in predetermined slot segments 80, in one circumferentialdirection as the radially outer or first layer 248 of stator winding 200and then reverses direction and winds around stator core 48 in theopposite circumferential direction as the radially inner or second layer269 of stator winding 200. When first straight portion 246 e extendsfrom first axial end 263, instead of extending from stator core 48 as asecond lead, it extends radially inwardly and connects to an end loopsegment, which enters slot number 401 in the radially inward or secondlayer 269 to connect to the straight portion 272 e.

While the stator winding has been shown and described as a three phasestator winding, those skilled in the art, however, will appreciate thatthe stator winding could be formed as a six phase winding or any otherpattern advantageous for producing electrical power or for generatingtorque, as in the case of an electric motor.

Further, while the stator winding has been shown as having two layersand therefore two conductors in each slot segment, it is often desirableto have a stator winding with more layers, such as four, and moreconductors in each slot. This can be achieved by installing a pluralityof layers substantially identical to first layer and second layer andradially alternating the windings substantially identical to first layerwith windings substantially identical with second layer, resulting in aplurality of layers and a plurality of conductors in each slot segment.

At this point it should be still further understood that the exemplaryembodiment provides a stator core having slot segments loaded withcontinuous conductors having a rectangular cross-section. The statorcore also includes tooth elements and tooth members that reduce a widthof the slot segments to less than a width of the continuous conductors.The stator core is at least twice deformed prior to completion. Morespecifically, a core member is first deformed in a first direction toallow the insertion of the continuous conductors and then deformed in asecond direction to establish a final geometry of the stator core.

While the invention has been described with reference to an exemplaryembodiment or embodiments, it will be understood by those skilled in theart that various changes may be made and equivalents may be substitutedfor elements thereof without departing from the scope of the invention.In addition, many modifications may be made to adapt a particularsituation or material to the teachings of the invention withoutdeparting from the essential scope thereof. Therefore, it is intendedthat the invention not be limited to the particular embodiment disclosedas the best mode contemplated for carrying out this invention, but thatthe invention will include all embodiments falling within the scope ofthe claims.

What is claimed is:
 1. A method of inserting a continuous conductorhaving a rectangular cross-section into slot segments formed in a statorcore, the method comprising: forming a core member extending from afirst end portion to a second end portion and a plurality of slotsegments each having an opening; inserting a stator winding having aplurality of phases into select ones of the slot segments, each of theplurality of phases having at least one conductor including a pluralityof substantially straight segments alternately connected by a pluralityof end loop segments, wherein a section of the at least one conductorincludes three consecutive end loop segments and three consecutivestraight segments formed from a single continuous conductor; andnarrowing the opening of each of the plurality of slot segments formingan annular stator core having a central axis, wherein the threeconsecutive straight segments are substantially similarly radiallyspaced from the central axis.
 2. The method of claim 1, furthercomprising: joining the first end portion of the core member to thesecond end portion of the core member to form the annular stator coreabout the central axis.
 3. The method of claim 1, further comprising:widening the opening of each of the plurality of slot segments byseparating tooth elements provided on the end portions of the slotsegments.
 4. The method of claim 1, wherein forming the core memberincludes deforming the core member in a first direction establishing aconvex curvilinear surface defined by end portions of the slot segments.5. The method of claim 1, further comprising deforming the core memberin a second direction to narrow the opening in each of the slotsegments.
 6. The method of claim 5, wherein deforming the core member inthe second direction establishes a concave curvilinear surface definedby the end portions of the slot segments.
 7. A stator core comprising: acore member having a first end portion that extends to a second endportion through a first surface and an opposing second surface, the coremember including a first axial end, a second axial end and a centralaxis; a plurality of slot segments formed in the core member, each ofthe plurality of slot segments including first and second wall portionsspaced one from another to define a first width of the plurality of slotsegments, each of the first wall portions including a first end portion,a second end portion, and a tooth element arranged at the second endportion, and each of the second wall portions including a first endsection, a second end section, and a tooth member at the second endsection, the tooth element on each first wall portion extending towardthe tooth member on each second wall portion to define a second width ofthe slot segment; and a stator winding having a plurality of phases,each of the plurality of phases having at least one conductor includinga plurality of substantially straight segments disposed in select onesof the plurality of slot segments, the straight segments beingalternately connected at the first and second axial ends of the coremember by a plurality of end loop segments, a section of the at leastone conductors includes three consecutive end loop segments and threestraight segments formed from a single continuous conductor, wherein thethree consecutive straight segments are substantially similarly radiallyspaced from the central axis.
 8. The stator core according to claim 7,wherein the first end portion is joined to the second end portion todefine an annular stator core about the central axis.
 9. The stator coreaccording to claim 7, further comprising a plurality of recesses formedin the second surface.
 10. The stator core according to claim 7, furthercomprising: a plurality of cooling passages extending through the coremember.
 11. An electric machine comprising: a housing; a rotor rotatablysupported within the housing; a stator fixedly mounted relative to therotor, the stator comprising: a stator core including a core memberhaving a first end portion that extends to a second end portion througha first surface and an opposing, second surface, the core memberincluding a central axis, a first axial end and a second axial end; aplurality of slot segments formed in the core member, each of theplurality of slot segments including first and second wall portionsspaced one from another to define a first width of the plurality of slotsegments, each of the first wall portions including a first end portion,a second end portion and a tooth element arranged at the second endportion, and each of the second wall portions including a first endsection, a second end section, and a tooth member at the second endsection, the tooth element on each first wall portion extending towardthe tooth member on each second wall portion to define a second width ofthe slot segment; and a stator winding having a plurality of phases,each of the plurality of phases having at least one conductor includinga plurality of substantially straight segments disposed in select onesof the plurality of slot segments, the straight segments beingalternately connected at the first and second axial ends of the coremember by a plurality of end loop segments, a section of the at leastone conductor includes three consecutive end loop segments and threestraight segments formed from a single continuous conductor, wherein thethree consecutive straight segments are substantially similarly radiallyspaced from the central axis.
 12. The electric machine according toclaim 11, wherein the first end portion of the core member is joined tothe second end portion of the core member to define an annular statorcore about the central axis.
 13. The electric machine according to claim11, further comprising: a plurality of recesses formed in the secondsurface of the core member.
 14. The electric machine according to claim11, further comprising: a plurality of cooling passages formed in thecore member.